粉煤灰干容重对动床模型试验的影响

Influence of Dry-Bulk Density of Fly Ash to the Movable Bed Model Test

为了保证模型冲淤相似并使动床模型试验结果具有较好的重复性,以郑州热电厂粉煤灰作为模型沙,从起动流速、冲刷率及坍落高度等方面分析了干容重对动床模型试验的影响。结果表明:①中值粒径为0.021 mm的细颗粒粉煤灰,水下固结时间对其起动流速有较大影响;中值粒径为0.056 mm的粉煤灰,水下固结时间对其起动流速影响很小;中值粒径0.106 mm的粗颗粒粉煤灰,起动流速已与水下固结时间无关。②粉煤灰冲刷率随冲刷时间的延长而逐渐减小;在同一进口条件和边界条件下,粉煤灰的冲刷率随干容重的增大而减小,但减小的幅度随干容重的增大而有所变缓;粉煤灰冲刷率随流量的增大而增大,但增大的幅度随流量的增大而有所变缓。③粉煤灰的沉积历时越长,临界坍落高度越大,而临界坍落高度增加的速率随暴露时间的延长而逐渐减小,临界坍落高度最终趋于一最大值;坍落稳定坡度随暴露时间的延长而增大,并逐渐趋于一最大值。

Fly ash in Zhengzhou thermal power plant as model sand, according to incipient velocity, flushing rate and slump, the influence of dry- bulk density to the movable bed model test is analyzed in this paper. The results are as follows ： a） When medium particle diameter is 0. 021 mm, consolidation duration underwater has a great influence to the incipient velocity. When medium particle diameter is O. 056 mm, consolidation dura- tion underwater has little influence to the incipient velocity. When medium particle diameter is O. 106 mm, incipient velocity has nothing to do withconsolidation duration underwater, b） With the extension of duration, flushing rate decreases. As for the same condition, with the increase ot dry- bulk density, flushing rate decreases, hut the decrease rate gradually decreases. With the increase of flow discharge, flushing rate increases, but increase rate also gradually decreases, c） With the increase of duration of sedimentation, critical slump increases, but the increase rate gradually decreases, and finally closes to a maximum value. With the increase of exposure duration, slump stable slope increases, and finally closes to a maximum value.